Short-wavelength probes in time-resolved photoelectron spectroscopy: an extended view of the excited state dynamics in acetylacetone

Abstract

Time-resolved photoelectron spectroscopy using a vacuum ultraviolet probe brings new insight to the excited state dynamics operating in acetylacetone.

Improved insights in time-resolved photoelectron imaging

“…Spectral signatures originating from three different electronic states are indicated. Figure adapted from Kotsina et al 76 to ionization from the hot S 0 ground state -populated from S 1 ( 1 A g ) -are also observed at energies o0.5 eV. This new information revealed by the multi-photon probe step is, however, seen only weakly in the photoelectron spectrum due to the reduced two-photon ionization probability relative to the competing (1 + 1 0 ) scheme.…”

“…Here, we present the basic incorporation of a relatively simple VUV source into our TRPEI spectrometer to convey the advantages of short wavelength probes through a case study on the molecule acetylacetone. 76 This makes use of an established methodology producing the fifth harmonic of a Ti:Sapphire laser (160 nm) in a static gas cell via non-collinear four-wave mixing. 77,78 Such an approach has also been demonstrated previously for use as a probe in other time-resolved studies of non-adiabatic molecular processes, [79][80][81][82] as have related variations employing the sixth harmonic (133 nm) [83][84][85][86] and ninth harmonic (90 nm).…”

“…A complete literature review of this subject is beyond the scope of this article and the reader is referred to our original publication for further details. 76 The key issue to highlight here, however, is that previous time-resolved studies have only reported quantitative measurements for different subsections of the overall excited state reaction coordinate. 75,[92][93][94][95] Fig.…”

“…6) are 13.90, 1.00, 0.92 and 0.91, respectively, assuming a laser pulse FWHM of 100 fs. Figure adapted from Kotsina et al 76 bands of the molecule under study to avoid this issue altogether. Unfortunately, satisfying this condition becomes challenging when employing a VUV probe as most molecules absorb strongly across the VUV region -although the differing nature of the pump and probe absorptions can potentially come to our aid here.…”

Ultrafast Photo‐ion Probing of the Ring‐Opening Process in Trans‐Stilbene Oxide

“…have shown that when probing molecules with states that possess a lifetime shorter than the duration of the laser pulse used to investigate it, one can still observe a signal from this state, but it will be significantly under‐sampled compared to longer‐lived states within the same system. [ 37 , 38 ] This led us to believe that the tall, narrow feature seen in Figure 4 could potentially be due to under‐sampling a very short‐lived state in stilbene oxide. To test this hypothesis, we performed a series of simulations, that are described extensively in the Supporting Information.…”